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New research challenges refuge concept and growers

Elton Robinson | May 03, 2004

MEMPHIS, Tenn. - Cotton producers should not relax their attitudes toward the current Bt cotton refuge requirements as an insect resistance tool, even though a new study indicates that plants and weeds other than cotton can also serve as refuges.

The recently completed alternate host project, which was funded by Monsanto and USDA, relied on an analysis tool which can reliably determine whether or not selected moths originated in cotton or in alternate hosts such as other crops or weeds. The study was conducted in five states in cooperation with state research groups and USDA and was recently submitted to EPA.

The study showed significant contributions of bollworm moths from non-cotton hosts throughout the season in all areas tested, according to Walt Mullins, Monsanto’s technical manager for Bollgard and Bollgard II. “In some areas the contribution was so large, that the question arose as to the significance of the role of the non-Bt cotton refuge in the system.”

New Bt technologies with different modes of action could also present a good argument for reviewing refuge requirements. Mullins noted that new technologies such as Bollgard II will place several new Bt proteins, combinations of proteins and new Bt modes of action in the field to battle resistance.

“Bollgard II contains two Bt genes which come from different Cry protein groups, meaning they work a little differently on target pests,” Mullins said. “This means it’s much less likely that you’re going to have a bollworm or budworm that’s resistant to both proteins than you are from the single protein.

“In addition, for tobacco budworms and pink bollworms each protein is an extremely effective dose individually. This creates an extremely high hurdle for a resistant insect. So now the requirement for the numbers of refuge or susceptible insects should decline significantly.

“As we develop this information, our intent would be to work with EPA to refine refuge policy and make it as convenient to growers as much as we possibly can,” Mullins added.

The conclusions present an interesting challenge for Monsanto and the cotton producers who use its technology.

“We want the grower to know that we will petition EPA for adjustment in refuges if it can be technically justified and is appropriate,” Mullins said. “Our objective is to maintain good resistance management without inconveniencing growers anymore than they need to be.

“But until research can technically justify a change, it’s important that Monsanto and growers work together to maintain compliance and appropriate stewardship.”

EPA has not indicated that it will review refuge requirements in light of the study.

Meanwhile, Monsanto continues to educate growers and monitor grower compliance. Each year, the National Cotton Council sends every registered Bollgard or Bollgard II user an insect resistance management brochure to keep the refuge requirements fresh in their minds, according to Mullins. “It also helps when university and Extension people talk about it and write about it in their newsletters and publications.”

Monsanto also makes random visits to farms every year. If this process finds a grower out of compliance, “we talk to him or her about the mistake and then revisit the grower the following year to make sure he or she understood what the corrections are,” Mullins said.

“Occasionally, we find a grower who doesn’t appear to have a good reason not to have a refuge. We visit that grower again the following year, and if we find the grower significantly out of compliance two years in a row, we remove the license for one year.”

Generally, growers are good about following through on compliance the year after being cautioned, according to Mullins, who can recall only a handful of cases where Bt technology was denied to a grower.

According to telephone surveys conducted for Monsanto, and also provided to EPA, approximately 90 percent of cotton producers surveyed over the last three years correctly follow resistance management requirements for Bt cotton.

Typically, most who were not in compliance made mathematical errors computing the size of their refuges, according to Mullins. “Others may say their refuge was hailed out or flooded out, and we generally give the growers the benefit of the doubt in those situations. However, we do revisit these growers the next year to confirm that these are not ‘recurring problems’.”

Based on the annual compliance survey, there was a slight decline in compliance in some specific areas. These areas were brought to EPA’s attention. In response, Monsanto will focus more of their compliance visits in those areas for 2004, and Mullins expects to see compliance improve accordingly.

For more information on the compliance program, growers can contact a local Monsanto representative or Monsanto at 1-800-ROUNDUP through EPA/Monsanto’s Compliance Assurance Program.